or Yan Chau Tong () is a harbour hugged by Double Island, Crescent Island and Crooked Island with north-eastern New Territories. It contains many deep red coloured rocks formed during a period of global warming in Tertiary. Oxidation rate of iron increased due to higher temperature and humidity, forming the iron oxide (rust) Port Island (), as the Chinese name Chek Chau implies, Port Island is a place of red earth. The ground on the entire island is rust-coloured conglomerate and siltstone formed similarly during Teritary. North and south coasts of Tolo Channel The area includes the north and south shores of Tolo Channel. The oldest rocks in Hong Kong, the Bluff Head formation, formed about 400 million years ago during the Devonian Period, are at the northeastern tip of the Tolo channel. Various deformation and erosion features can be seen from these rocks. One of the famous features is the Devil's fist formed by weathering and erosion along the sandstone bedding forming the shape of the “Ghost fingers”. Ma Shi Chau () presents the sedimentary rocks formed about 280 million years ago. Various fossils such as ammonites, corals and bivalves were found on Ma Shi Chau. Sitting right next to the Tolo Channel fault system, various sheared features and folds can be observed. Lai Chi Chong () showcases various volcanic rocks and sedimentary rocks formed about 146 million years ago. The siltstone beds were interbedded with volcanic tuffite. Tuffite is a sedimentary rock with a volcanic origin. It formed by fine volcanic ash deposited in water, forming a sedimentary bed of volcanic ash. Other than that, there is also a black cherty mudstone on Lai Chi Chong, which is believed to be formed by mud deposited together with silica-rich materials. The black color indicated an oxygen depleted deposition environment. These black mudstones beds exhibits a slump fold structure. Large coherent mass of loosely consolidated materials might have slid down along a slope and folded the mudstone beds. Tung Ping Chau Tung Ping Chau () sits in Mirs Bay in northeastern Hong Kong. It is the easternmost outlying island of Hong Kong. Tung Ping Chau is a popular holiday destination for locals. Its attractions, such as wave erosion landscape, the shale that resembles a sponge cake structure and the unusually flat lay of the island itself, draw thousands of visitors annually. See also Geology of Hong Kong Conservation in Hong